"I didn't want to go on stage tonight, I really didn't, but these people bought tickets, they came and wanted to have a good time and I remembered that," said Mafi.

When Ali first met Williams, he could believe what a down to earth-kind of person he was.

"When he introduced himself he goes, 'Hi I'm Robin Williams,' as if I didn't know this legend was in front of me. It made me realize that this was a really humble person who cared about his craft. He was really a nice guy," recalls Mafi.